Summary BENZENES:-STRUCTURE,RINGS,NAMING

Organic Lecture Series




Reactions of
Benzene &
Its Derivatives
Chapter 22 1




Organic Lecture Series

Reactions of Benzene
The most characteristic reaction of
aromatic compounds is substitution at
a ring carbon:
Halogenation:
Fe Cl 3
H + Cl 2 Cl + HCl

Chlorobenzene
Nitration:
H2 SO 4
H + HN O 3 N O2 + H2 O

Nitrobenzene
2

, Organic Lecture Series
Reactions of Benzene
Sulfonation:
H2 SO4
H + SO3 SO3 H

Benzenesulfonic acid

Alkylation:
A lX 3
H + RX R + HX

An alkylbenzene

Acylation:
O O
A lX 3
H + RC X CR + HX

An acylbenzene
3




Organic Lecture Series




Carbon-Carbon Bond Formations:

R
R Cl

AlCl3

Arenes Alkylbenzenes
4

, Organic Lecture Series


Electrophilic Aromatic Substitution
• Electrophilic aromatic substitution: a
reaction in which a hydrogen atom of an
aromatic ring is replaced by an
electrophile
H E
+
+ E + H+


• In this section:
– several common types of electrophiles
– how each is generated
– the mechanism by which each replaces
hydrogen
5




Organic Lecture Series

EAS: General Mechanism
• A general mechanism
s low , rate +
+
determin ing H
Step 1: H + E
E
Electro- Res on ance-s tabilized
phile cation intermed iate
+
H fast +
Step 2: E + H
E


• Key question: What is the electrophile and
how is it generated?
6